mcnaney



March 24, 1964 J. T. M NANEY 3,126,548

ELECTROSTATIC DATA RECORDING APPARATUS Filed Dec. 18, 1961 2 Sheets-Sheet 1 INVENTOR.

United States Patent Ofi ice 3,126,548 Patented Mar. 24, 1964 3,126,548 ELECTROSTATIC DATA RECORDING APPARATUS Joseph T. McNaney, 8548 Boulder Drive, La Mesa, Calif. Filed Dec. 18, 1961, Ser. No. 160,705 18 Claims. (Cl. 346-74) This invention relates to electrostatic data recording apparatus and more particularly to apparatus of this type which is designed to provide recordings on ordinary writing paper in response to light intormation.

Electrostatic data recording apparatus responsive to light information have been in use for a number of years. Although advances in the art have been made, these apparatus nevertheless have characteristic limitations. They generally require intermediate storage means from which a developing powder adhering to latent images must be transferred, requiring continual wiping away of a remaining powder prior to the exposure of such storage means to further light information and subsequent formation of latent images thereon. This storage means is usually in the form of a drum, or a plate, supporting a thin layer or photoconductive material which must be subjected to the continual wiping away of the remaining powder which, in turn, subjects such storage means to a relatively short life. Because of this undesirable aspect it would be highly desirable to avoid the necessity of having to wipe away the remaining powder and, thereby, avoid the costs and complexity involved.

Accordingly, it is an object of this invention to provide an improved apparatus for converting light information into a recording on ordinary paper media.

It is an object of this invention to eliminate the necessity of wiping excess developing powder from the surface of an intermediate storage means in an electrostatic data recording apparatus.

It is another object of this invention to circumvent the requirement of attaching developing powder to a latent image.

It is a further object of this invention to provide an improved means of. converting light information into a recording thereof.

It is a further object of this invention to provide an improved means of depositing developing powder on a record media in response to light information.

Further objects and a fuller understanding of the invention will become apparent with reference to the following description and claims, taken in conjunction with the accompanying drawings in which:

FIGURE 1 is an illustration of one embodiment of the invention wherein a light responsive switch means is utilized in a system for scanning a source of light information and a recording means;

FIGURE 2. is an illustration of another embodiment of the invention wherein a source of light information and a recording means is displaced in relation to a fixed positioned light responsive switch means;

.FlGURE 3 is an illustration of another embodiment of the invention wherein a light responsive switch means is shown in partial sectional and plan views, namely, a

and b, representing a panel array as utilized in a recordof refraction, a light conducting jacket 12 having an index of refraction being less than the predetermined index of refraction of the fiber '11, and an adjoining layer 13 of photoconductive material. In FIGURES 1 and 2 the plurality of fibers 11 are supported in a single line array in switch means 10, being bonded together by means of an electrical insulating material 14. In FIGURES 3, 4 and 5 the plurality of fibers 11 are supported in a panel array in switch means 10, also bonded together by means of an electrical insulating material 14.

Each light conducting fiber 11 of each light responsive switch means 10 has a longitudinal dimension exceeding its cross sectional dimension and an outer surface general-ly along its longitudinal dimension, and a predetermined index of refraction. The light conducting jacket 12 of each fiber 11 has an index of refraction less than said predetermined index which coats a major par-t of the outer surface to which surface the jacket is intimately joined to form an interface along the juncture. The layer 13 of photoconductive material, such as selenium, cadmium sulphide, silver selinide, and like materials, extends longitudinally along the outer sunface of the fiber 11, whereby, light waves entering the fiber 11 will be reflected to the photoconductor layer 13 along its longitudinal dimension by means of the jacket 12.

The longitudinal dimension of the layer 13 is designed, when in a dark non-conductive state, to be of a length necessary to prevent the influence of a potential being connected to one end thereof from reaching the opposite end, The conversion of layer 13 from a non-conductor to a conductor of electrical energy will be accomplished by illuminating it with light waves being reflected to its inner surface from the interface of the fiber 11 and the jacket 12. The etficient conduction of light waves through the fiber 11 for the purpose of illuminating the layer 13 along its longitudinal dimension depends on the light reflecting capabilities of the jacket 12. Unless the fiber 11 is jacketed with a material which has an index of refraction less than the index of the fiber, light waves entering one end thereof will either escape from the fiber 11 into an adjacent medium if it is of a higher index, or, be absorbed by an adjacent medium if it is opaque in character. Since the longitudinal dimension of the fiber 11 exceed-s its cross sectional dimension a great number of times, for example the cross sectional dimension may be less than 0.001" and the longitudinal dimension may be more than a few tenths of an inch, the lower index jacket 12 will permit light waves entering one end of the fiber 11 to be conducted to the opposite end by means of internal reflections which occur after the light waves have penetrated to jacket 12 and beyond the interface. Due to a spiralling and scattering of reflected light waves during their travels along the longitudinal dimension of the fiber 11, a required percentage of the total amount of light energy will be permitted to reach the layer 13, to thereby illuminate the layer 13 along a longitudinal dimension thereof.

*In the FIGURE 1 embodiment of the invention the light responsive switch means 10 is shown greatly enlarged in relation to other essential elements in the illustration for the purpose of providing an adequate description of the invention. Since in this embodiment the switch means 10 utilizes a single line of fibers 1.1, such an array of fibers 1 1 lends itself to the ability of applying the layer 13 to each fiber 11 in the form of a unitary layer extending from one end 16 of the switch means 10 to the opposite end '18. Under these circumstances the layer 13 would be applied after the plurality of fibers 11 have been assembled in the array as indicated. However, the invention is not to be limited to this particular procedure of fabrication. Although the fibers 1.1 are shown to be rectangular in cross section, these fibers 11 may, of

course, be round, oval, or of any other desired cross sectional shape.

The switch means in FIGURE 1 is provided with a first conductor 29 operatively connected to a first tend, respectively, of layers 13. Although this first end 22 is represented as being closely adjacent the one end 23 of the fibers 11, it is entirely within the scope of the present invention to extend the length of the fiber 11 beyond that of its layer 13. It will of course be understood by those skilled in the arts that it may be desirable to have the fibers 11 made of lengths which are entirely independent of layer 13 lengths. A second end 24 of layers 13 is positioned closely adjacent a dielectric medium 26 having a first surface 23 and a second surface 29. The medium 26 is preferably a thin material having exceptionally high electrical resistance characteristics in combination with the ability to pass with a high degree of efiiciency the lines of force of an electrostatic field. Such properties will be found in rubber, glass, nylon, Vinylite materials and the like;

When utilized in a system of data recording the dielectric medium 26 will bee'lectrostatically polarized and have applied to the first surface thereof a layer of oppositely charged particles of a developing powder. The layer of particles 30 will be deposited uniformly over the first surface 28. A second conductor 32 will be spaced apart from the layer of particles 30, defining an air gap 34 'therebetween. A record medium 36 will be located within the air gap 34 and supported by the second conductor 32. A source of potential 38 will be connected between the first conductor 20 and the second conductor 32. Light energy will be derived from a source of light information 40, such as that which may be obtained from photographic film or from the reflections of an illuminated copy of recorded data.

Light information from the source 40 is shown, for example, being admitted to fibers 11a, 11c and 11c, and not to fibers 11b and 11d. Under these conditions light waves will be permitted to illuminate and thereby make electrically conductive layers 13 associated, respectively, with fibers 11a, 11c and 11e, while the remaining area of the photoconductive material 13 resists the flow of electrical energy, as I have indicated symbolically. The electrically conductive layers 13 of the fibers 11a, 11c and He will extend the potential of the source 38 to the second end 24 thereof, and also a potential influence of the source 38 across the air gap 34 adjacent the second end 24 respectively of layers 13 of the fibers 1101, 11c and 11e. Those powder particles 30a of the layer 30 being subjected to apotential influence will be repelled from the first surface 28 of the dielectric medium 26 and deposited on the record medium 36. Movement of the light responsive switch 10 in the direction of arrow 41 in relation to fixedly positioned light information 40, dielectric medium 26 and record medium 36 will permit a recording of the light information to be made in the form of selective deposits of powder particles on the record medium 36 corresponding with the light information received. After a record of the light information has been made in this manner the particles of powder may be fixed to the record medium 36 by well known means such as heat, or, by pressing the particles into the medium by subjecting them to a mechanical force.

Referring now to FIGURE 2, the light responsive switch means 10 is again shown in relation to a dielectric medium 26, a recordmedium 36, and a second conductor which is indicated in this illustration as being in the form of a roller 42.. A source. of light information 40 has not been included in this illustration, however, when in operation this embodiment will respond 'to light information in a manner similar to the description given of the initial embodiment. In FIGURE 2 the source of light information, the dielectric medium 26, and the record medium 36 will be allowed to move simultaneously in the direction of arrow 44, while the light responsive switch means ltl remains in a fixed position.

A means of applying a uniform layer of developing powder to the first surface '23 of the dielectric medium 26 is shown as consisting of a receptacle 46 of electrostatically charged electroscopic powder particles 48. The receptacle 46 is connected toa negative polarity of the source of potential 33, and an electrostatic polarizing element 5! is supported adjacent the second surface 29 of the dielectric medium 26 and is connected to a positive polarity of the source of potential 38. The element St is shown as being directly opposite the receptacle 46 on the opposite side of the dielectric medium 26. When in operation, the medium 26 is subjected to a positive polarization from the element 50 which causes a layer of negatively charged particles from the receptacle 46 to :be attracted and adhere to the first surface 28 of the medium 26. An agitator 5?. is permitted to rotate and bring the particles in contact with the charged medium 26 while both the dielectric medium 26 and the record medium are moved in the direction of the arrow 44. In accordance with my description of FIGURE 1, the powder particles will be repelled from the first surface 28 of the dielectric medium 26 and deposited on the record medium 36 as .both media move past the second end 24 of the illuminated layers 13 of their respective fibers 11. The selective illumination of layers 13 extends the potential influence of a negative polarity to a layer of particles which are also negatively charged, permitting the particles to be selectively repelled and deposited on the record me d ium whereupon the particles will be fixed to the medium 36 after passing over a heater unit 54.

In FIGURE 3 another embodiment of the invention is shown wherein the light responsive switch means 10 is in the form of a panel array. Each of the light conducting fibers have a predetermined index of refraction, a longitudinal dimension exceeding its cross sectional dimension and an outer surface generally along its longitudinal dimension. Each of the fibers 11 are also provided with a light conducting jacket 12 having an index of refraction which is less than the predetermined index or the fiber 11 and which is intimately joined with the outer surface of the fiber 11, forming a smooth interface along the juncture. At a, a cross section of several fibers 11 are shown, and at b, a plan View of a section of a panel array is shown, including an enlargement of a single fiber 11, its jacket 12, and a layer of photoconductive material 13. The jacket 12 is designed to essentially surround the fiber 11, however, the thickness dimension of the jacket varies in the direction of the jackets circumference. For example, the jacket thickness at the least dimension will be less than one micron, while at the greatest dimension the jacket thickness will be in excess of ten microns. In the process of drawing the jacketed fiber down from much larger glass rods the inner rod of higher-refraction glass will be inserted in a tubing of lower-refraction glass and the two materials, both rod and tubing, will be drawn together. However, the ratio of wall thickness on one side of the tubing to wall thickness on the opposite side of the tubing will be greater than 10 to 1.

The object of the jacketed fiber illustrated in this embodiment is to utilize the predetermined thickness dimensions of the jacket 12 to control the conduction of light waves through the fiber 11 and the conduction of light waves to the photoconductive layer 13 as a function of wavelength. Since light wave penetrations into the jacket 12 are estimated to be a little more than a wavelength from the interface a light wave of a given wavelength may be reflected by the jacket 12 at one point by reason of a wavelength-to-jacket thickness relationship, but penetrate the jacket at a point where the thickness is equal to a wavelength or less. Although I prefer to show a layer 13 of photoconductive material deposited on the entire outer surface of the jacket 12, light waves will be permitted to reach the layer 13 on the one side of the fiber 11 where the jacket 12 thickness dimension permits the passage of light waves therethrough.

In this embodiment the layer 13 is extended from a first end 55 of fiber 11 to a second end 56 thereof, and the array of fibers 11 are supported in a side-by-side arrangement by means of a bonding material 14, which is also a good electrical resistor. A first surface coinciding with the first end 55 of the fibers 11 has deposited thereon a layer of light transparent electrically conductive mate rial 58. An example of a well known material 58 that may be used for this purpose is produced by Pittsburgh Plate Glass (30., under the name of Nesa transparent conductive material. A surface coinciding with the second end 56 of the fibers 11 has deposited thereon a layer of dielectric material 60 which is preferably a thin material having exceptionally high electrical resistance capabilities in combination with the ability to pass with a high degree of efficiency the lines of force of an electrostatic field. The layer 60 may also be in the form of a photoconductive material.

The light responsive switch means as described thus far represents a sandwich like structure, when not exposed to light, presenting a high electrical resistance between the first layer 58 and a second layer 60. However, when exposed to light information the potential influence of a source of potential connected to the first layer 58 may be extended selectively to the second layer 60. As illustrated, an electrode 32 is spaced apart from the switch means 10, providing an air gap 34 between the second layer 60 and the electrode 32. When used in a recording apparatus a uniform layer of powder particles will be deposited on the surface 62 of the second layer 66, and a record medium 36 will be positioned within the air gap 34 intermediate the layer of powder particles and the electrode 32. A source of potential 38 will be con nected between the layer 58 and the electrode 32, and a negative potential influence will be extended selectively, in response to the light information received, to the layer of particles whereupon particles will be repelled selectively from the surface 62 of the second layer 69, and deposited on the adjacent record medium 36.

In FIGURE 4 a plan view of a section of a light responsive switch 10 is shown which may be utilized in the type of recording apparatus described in conjunction with FIGURE 3. In this switch 10 embodiment the light conducting fibers 11, the jacket, and the photoconductive layer 13, represent a form of construction very similar to that shown and described in conjunction with FIGURES l and 2. When in operation, the end result will be comparable with that of the switch means 10 embodiments of FIGURES 1, 2 and 3.

Referring now to FIGURE 5, the light responsive switch means 10 of FIGURES 3 and 4 is shown in a more complete system of data recording. At a, the layer 60 of the switch means It) will be electrostatically polarized, positive for example, 'by means of an ion charge generator 61. At b, the layer 60 will have deposited thereon a uniform layer of negatively charged powder particles 63 which will, for example, be sprayed on layer 60 from a source 64. At 0, the switch means 10 is shown positioned adjacent the record medium 36. In this latter position powder particles from a layer 65 of such particles will be selectively repelled from the switch means 10 and thereby selectively deposited on the record medium 36 in accordance with the light information exposed to the surface 66 of the switch means 10.

It should be understood that if the developing powder referred to in the foregoing discussion is, for example, black in color a negative copy will be made of the original light information. However, the use of a black record media and white developing powder would provide a positive copy of this page of written matter, as an example. A further method of providing a positive copy of an or'iginal'copy would require the removal of the record medium 36, from the position shown in FIGURE 50, during the period of time light information is being exposed to the surface 66 of the switch means 10. In a following step in the operation a positive image of the original copy, remaining on the layer 60 of the switch means 10, would be deposited on the record medium 36 upon the exposure of an auxiliary beam of light to the entire area of the surface 66. A positive image of the original copy appearing on the layer 69 will be repelled therefrom and deposited on the medium 36.

It should, of course, be understood that many of the other embodiments embracing the general principles of the constructions hereinbefore set forth may be utilized and still be within the ambit of the present invention.

The particular embodiments of the invention illustrated and described herein are illustrative only, and the invention includes such other modifications and equivalents as may readily appear to those skilled in the arts, and within the scope of the appended claims.

I claim:

1. In an apparatus for selectively repelling electrostatically charged particles from an electrostatically charged surface in response to light information,

(a) a source of potential,

(b) first and second conductors,

(0) means for connecting said conductors to opposite terminals of said source,

(d) light responsive switch means including a plurality of light conducting fibers each having a predetermined index of refraction, a longitudinal dimension exceeding its cross sectional dimension and an outer surface generally along its longitudinal dimension,

each of said fibers being provided with a light conducting jacket having an index of refraction less than said predetermined index and coating part of the outer surface of said fiber and intimately joined therewith,

each of said fibers being provided with a longitudinally extending layer of photoconductive material disposed upon and intimately joined with an uncoated part of the outer surface of said fiber and having first and second ends,

(e) the first end of said layers being operatively connected to said first conductor,

( the second end of said layers being spaced apart from said second conductor,

(g) said electrostatically charged surface being adjacent said second ends of said layers and adapted to support a layer of said electrostatically charged particles,

(h) said jacket of each said fibers being adapted to control the reflection of light information to said photoconductive material whereby a potential influence from said source will be extended to the layer of charged particles thereby said particles will be reflected from said charged surface.

2. In an apparatus for selectively repelling electrostatically charged particles from an electrostatically charged surface in response to light information,

(a) first and second electrical conductor members having a potential impressed thereacross,

(b) a source of light information,

(0) a light responsive switch means comprising a plurality of light conducting fibers, each having a predetermined index of refraction, a light conducting jacket having an index of refraction less than said predetermined index, and a layer of photoconductive material adapted to receive light information being reflected from said jacket,

(d) a dielectric medium, adapted to receive an electrostatic charge, positioned adjacent said light responsive switch means,

(e) means for depositing a layer of said electrostatically charged particles upon an electrostatically charged surface of said dielectric medium,

(f) said light responsive switch means being adapted to discharge said potential selectively between said first and second conductors in response to said light information to thereby neutralize selectively said electrostatically charged dielectric medium whereby electrostatically charged particles will be repelled selectively therefrom.

3. In an apparatus for selectively repelling electro statically charged particles from a dielectric medium in response to light information,

(a) a light responsive switch means including a light conducting fiber having a predetermined index of refraction, a longitudinal dimension exceeding its cross sectional dimension and an outer surface generally along its longitudinal dimension,

a light conducting jacket having an index of refraction less than said predetermined index coating part of the outer surface of said fiber and intimately joined therewith,

a longitudinally extending layer of photoconductive material disposed upon and intimately joined with an uncoated part of the outer surface of said fiber and having first and second ends,

([1) a dielectric medium positioned adjacent said second end of said layer,

() means for effecting a uniform electrostatically charged condition upon a surface of said medium,

(d) means for depositing a layer of said electrostatically charged particles upon said surface of said medium,

(e) a first electrode connected operatively with said layer adjacent said first end.

(f) a second electrode spaced apart from said layer of electrostatically charged particles,

(g) a source of potential connected between said first and second electrodes,

. (It) means for exposing said light responsive switch to said light information whereby a potential influence of said source of potential will be applied to said medium causing particles to be repelled therefrom.

4. In a recording apparatus,

(a) first and second electrical conductors having a potential connected thereacross,

(b) a source of light information,

(0) light responsive switch means including a plurality of light conducting fibers each having a predetermined index of refraction, a longitudinal dimension exceeding its cross sectional dimension and an outer surface generally along its longitudinal dimension,

said plurality of fibers each being provided with a light conducting jacket having an index of refraction less than said predetermined index and coating part of the outer surface of said fiber and intimately joined therewith,

said plurality of fibers each being provided with a longitudinally extending layer of photoconductive material disposed upon and intimately joined with an uncoated part of the outer surface and having first and second ends,

(d) thefirst end of said layers of said switch being operatively connected to said first conductor,

(e) the second end of said layers of said switch being spaced apart from said second conductor defining an air gap therebetween, v

(f) a record medium being located within said air gap adjacent said second conductor,

(g) a dielectric medium being located within said air gap adjacent said second end of the layers of said switch,

(11) a layer of electrostatically charged particles disposed upon said dielectric medium within said air p and (i) means for exposing said light responsive switch to said light information whereby a potential influence of said source of poteiitial will be exerted on said particles causing said particles to be selectively repell'ed from said dielectric medium and deposited on said record medium,

5. The invention as set forth in claim 4 additionally including,

(j) means for supporting said plurality of fibers in a single line array, and (k) means for scanning said light information and said dielectric medium simultaneously with said rray thereby depositing said particles on said record medium corresponding to an image of said light information. 6. The invention as set forth in claim 4 additionally including,

(j) means for supporting said plurality of fibers in a single line array, and

(k) means for providing a lineal movement of said light information in relation to said switch means simultaneously with lineal movements respectively of said dielectric medium and said record medium in relation to said switch means.

7. The invention as set forth in claim 4 additionally including,

(j) means for, selectively effecting a uniform electrostatic polarization of said dielectric medium and applying a layer of electrostatically charged particles to said dielectric medium.

8. The invention as set forth in claim 4 additionally including,

(j) means for fixing to said record medium said particles selectively repelled from said dielectric medium and deposited on said record medium.

9. The invention as set forth in claim 4 additionally including,

(j) means for supporting said plurality of fibers in a panel array, providing a smooth panel surface adjacent said second ends, and

(k) a layer of dielectric medium disposed upon and intimately joined with said smooth panel surface.

10. A device which is designed for use in a recording apparatus comprising a sandwich like structure including,

'(c) said plurality of fibers each being provided with a longitudinally extending layer of photoconductive material disposed upon and intimately joined with an uncoated part of the outer surface of each fiber and having first and second ends,

(d) said plurality of fibers being arranged in a panel array, including means for securing said fibers into said array, providing first and second surfaces,

(e) a layer of light transparent electrically conductive material disposed upon said first surface and operatively connected with said first ends of said photoconductive material, and

(f) a layer of dielectric material disposed upon said second surface adjacent said second ends of said photoconductive material.

11. A device which is designed for use in a recording apparatus comprising a sandwich like structure including,

(a) a plurality of light conducting fibers each having a predetermined index of refraction, a longitudinal dimension exceeding its cross sectional dimension and an outer surface generally along its longitudinal dimension, 7

(b) said plurality of fibers each being provided with a light conducting jacket having an index of refrac- 9 tion less than said predetermined index and coating part of the outer surface of each fiber and intimately joined therewith,

said plurality of fibers each being provided with a longitudinally extending layer of photoconductive material disposed upon and intimately joined with an uncoated part of the outer surface of each fiber and having first and second ends,

(d) said plurality of fibers being arranged in a panel array, including means for securing said fibers into said array, providing first and second surfaces,

(e) a layer of light transparent electrically conductive material disposed upon said first surface and operatively connected with said first ends of said photoconductive material, and

(f) a layer of photoconductive material disposed upon said second surface and operatively connected with the second end-s of said photoconductive layers disposed upon said fibers.

12. The invention as set forth in claim 11 additionally including,

(g) means for eifecting a uniform electrostatic polarization of said layer of photoconductive material disposed upon said second surface of said panel array, and

(h) means for depositing a layer of electrostatically charged particles on said layer of photoconductive material on said second surface.

13. The invention as set forth in claim 12 additionally including,

(i) an electrode spaced apart from said layer of electrostatically charged particles defining an air gap therebetween,

(j) means for establishing the influence of an electrical potential between said light transparent electrically conductive layer and said electrode, and

(k) means for extending said influence selectively across said air gap whereby particles of said layer of charged particles will be repelled selectively from said layer of photoconductive material on said second surface.

14. The invention as set forth in claim 13 additionally including,

(1) a record medium within said air gap intermediate said iayer of charged particles and said electrode whereby said particles being selectively repelled from said layer of photoconductive material will be deposited on said record medium.

15. The invention as set forth in claim additionally including,

(g) an electrode spaced apart from said layer of dielectric material defining an air gap therebetween, (/1) means for establishing the influence of an electrical potential between said light transparent electrical conductor layer and said electrode, and

(i) means for extending said influence selectively across said air gap. 7

1 6. The invention as set forth in claim 15 additionally including,

(j) means for effecting a uniform electrostatic polarization of said layer of dielectric material, and

k) means for altering the uniform electrostatic polarization of said layer of dielectric material upon the extention of said potential influence across said air p- 17. A device which is designed for use in a recording apparatus comprising a sandwich like structure including,

(a) a plurality of light conducting fibers each having a predetermined index of refraction, a longitudinal dimension exceeding its cross sectional dimension, a longitudinally extending outer surface, and first and second ends,

(b) said plurality of fibers each being provided with a light conducting jacket having an index of refraction less than said predetermined index and intimately joined with said outer surface, and presenting an outer surface,

(0) said plurality of fibers each being provided with a longitudinally extending layer of photoconductive material disposed upon and intimately joined with said outer surface of said jacket,

(d) said plurality of fibers being arranged in a panel array wherein said first and second ends provide first and second surfaces, respectively, of said panel array,

(e) a layer of light transparent electrically conductive material disposed upon said first surface and operatively connected with said photoconductive material, and

(f) a iayer of dielectric material disposed upon said second surface and operatively joined with said photoconductive material,

(g) said jacket having predetermined thickness dimen sions and thereby adapted to control, selectively, the reflection of light waves to the fiber and the admittance of light waves to the layer of photoconductive material.

18. The invention as set forth in claim 17 additionally including,

(h) said layer of dielectric material having photoelectric properties whereby in a dark state layer resists the flow of electrical current and while in an illuminated state said layer is a conductor of electrical current.

References Cited in the file of this patent UNITED STATES PATENTS 

1. IN AN APPARATUS FOR SELECTIVELY REPELLING ELECTROSTATICALLY CHARGED PARTICLES FROM AN ELECTROSTATICALLY CHARGED SURFACE IN RESPONSE TO LIGHT INFORMATION, (A) A SOURCE OF POTENTIAL (B) FIRST AND SECOND CONDUCTORS, (C) MEANS FOR CONNECTING SAID CONDUCTORS TO OPPOSITE TERMINALS OF SAID SOURCE, (D) LIGHT RESPONSIVE SWITCH MEANS INCLUDING A PLURALITY OF LIGHT CONDUCTING FIBERS EACH HAVING A PREDETERMINED INDEX OF REFRACTION, A LONGITUDINAL DIMENSION EXCEEDING ITS CROSS SECTIONAL DIMENSION AND AN OUTER SURFACE GENERALLY ALONG ITS LONGITUDINAL DIMENSION, EACH OF SAID FIBERS BEING PROVIDED WITH A LIGHT CONDUCTING JACKET HAVING AN INDEX OF REFRACTION LESS THAN SAID PREDETERMINED INDEX AND COATING PART OF THE OUTER SURFACE OF SAID FIBER AND INTIMATELY JOINED THEREWITH, EACH OF SAID FIBERS BEING PROVIDED WITH A LONGITUDINALLY EXTENDING LAYER OF PHOTOCONDUCTIVE MATERIAL DISPOSED UPON AND INTIMATELY JOINED WITH AN UNCOATED PART OF THE OUTER SURFACE OF SAID FIBER AND HAVING FIRST AND SECOND ENDS, (E) THE FIRST END OF SAID LAYERS BEING OPERATIVELY CONNECTED TO SAID FIRST CONDUCTOR, (F) THE SECOND END OF SAID LAYERS BEING SPACED APART FROM SAID SECOND CONDUCTOR, (G) SAID ELECTROSTATICALLY CHARGED SURFACE BEING ADJACENT SAID SECOND ENDS OF SAID LAYERS AND ADAPTED TO SUPPORT A LAYER OF SAID ELECTROSTATICALLY CHARGED PARTICLES, (H) SAID JACKET OF EACH SAID FIBERS BEING ADAPTED TO CONTROL THE REFLECTION OF LIGHT INFORMATION TO SAID PHOTOCONDUCTIVE MATERIAL WHEREBY A POTENTIAL INFLUENCE FROM SAID SOURCE WILL BE EXTENDED TO THE LAYER OF CHARGED PARTICLES THEREBY SAID PARTICLES WILL BE REFLECTED FROM SAID CHARGED SURFACE. 